[sdiy] Shielding

[James Patchell]

Another good choice for voltage references is the LM4041-ADJ

You can see how I used this part in this VCO:

http://www.oldcrows.net/~patchell/synthmodules/100-1007.pdf

I agree with Harry, shielding will not actually affect stability.  If you 
get cross coupling, it will just sound nasty (unwanted 
modulation).  Generally, what I do when wiring my front panels is I use a 
twisted pair shielded cable for the signals (sine, tri, ramp, pulse), and 
for the sync input.

The rest of the inputs (CV) are just plain wires.  Now, the only other 
thing I do is provide a complete circuit for each jack/pot.  That is, there 
is always a return wire with each signal wire.  I do this even on panels 
where the jacks are electrically connected to the panel.  So far, this has 
worked out OK for me...but there are a lot of opinions on how this should 
be done.

On my latest project, because all of the jacks and pots are mounted on PC 
boards, everything is isolated from the panel.  But also, there are not 
flying wires going to the panel either....

At 07:47 PM 1/4/2004 -0500, harrybissell wrote:
>I don't think the shielding on the CVs would be as important as
>making a stable, low noise supply for the voltages fed to the pots.
>
>I like to use Zener diode shunt regulators on each module... so I burn
>a couple mA and get a really stable 10V reference.  If you are real fussy,
>you be sure to use references that are temperature stable as well...
>
>H^) harry
>
>MAKoot MAKoot wrote:
>
> > Hi all,
> > While working on my ASM-1 modular projekt I'm really intending to make the
> > SNR as high as possible, preferably MOTM-quality :)
> > So a question popped up while I was doing the wiring of the pots on the VCO
> > module to make them shielded or not. Sure we are speaking of CV voltages in
> > the range of appr. -10 to +10 volts, but I also have read that when 
> trying to
> > build a polyphonic synth, it really comes close in having a stable VCO.
> > So would anyone know if the fact to shield all the lines to the pods is
> > rubbish, or that it does make a difference? And is there maby a site or 
> something
> > somewhere with more information about avoiding noise?
> >
> > P.S. Could anyone maby point me to some good circuits of formant-filters on
> > the net? That'd be also great!
> >
> > P.S.2 I actually have read that the Doepfer VCO's are worse than the
> > ASM-1's. Is this really true?
> >
> > Thanks in advance!
> > Michiel
> >
> > --
> > +++ GMX - die erste Adresse für Mail, Message, More +++
> > Neu: Preissenkung für MMS und FreeMMS! http://www.gmx.net

         -Jim
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